It’s easy to forget just how quickly Led Zeppelin went from sharply juxtaposing blues thump with delicate folk on their debut to blending the two sounds seamlessly at once. After releasing three masterfully multidimensional LPs in 1969 and 1970, the group began its middle period relatively early, in 1971, with the release of its untitled fourth album.

That record remains Led Zeppelin’s masterpiece because it showcases everything the band did best – acoustic flourishes, heavy blues, insightful poetry, tawdry catcalls – in equal measure. From Robert Plant’s lascivious howling on the blues romp “Black Dog” to folk singer Sandy Denny trading verses with Plant amid plinking mandolin on “The Battle of Evermore,” and from the churning boogie-woogie of “Rock and Roll” to the guitar sludge of “Four Sticks” – all of which coalesced on “Stairway to Heaven” – the band never arrived at a better balance of their otherwise disparate interests.

The latest reissue of the album spotlights its sonic depth, thanks to illuminative remastering by guitarist-producer Jimmy Page, and, on the deluxe edition, alternate mixes of each track. A darker-sounding “Stairway to Heaven,” mixed in L.A., illustrates its mournfulness, a hypnotically instrumental “The Battle of Evermore” somehow makes the song more meditative and a stockier, drum-rattling “When the Levee Breaks” flexes its blues power. This time, all that glitters surely is gold.

The band’s follow-up album, 1973’s Houses of the Holy, presents Led Zeppelin at the height of confidence and willing to experiment. Although riff workouts like “The Ocean” and “The Song Remains the Same” caught the band flexing familiar muscles, the tracks that made the group’s fifth LP a triumph were the ones where they took risks: the woozy sliding guitars of “Dancing Days,” the twee blue-eyed reggae of “D’yer Mak’er,” the slippery funk of “The Crunge,” the jazzy mysticism of “No Quarter.” Decades of classic-rock radio saturation have made some of these songs canon, but when put in the context between Led Zeppelin’s fourth record and the double-LP deep dive that was Physical Graffiti, they reveal a band eager for change.

As with the reissue of the group’s fourth album, Page has impeccably restored the glimmer of Houses of the Holy and uncovered an LP’s worth of fascinating outtakes that show the band’s headspace at the time. An instrumental mix of “The Song Remains the Same” comes off as a guitar extravaganza, while a version of “No Quarter” underscores the track’s otherworldly qualities. Rough mixes of “The Crunge” and “Dancing Days” don’t reveal much more than alternate views of the versions that made the final LP, but a “working mix” of “The Ocean” feels a little freer, thanks to Plant’s louder shoo-bop, doo-wop backup vocals in the outro. It would take Led Zeppelin another two years to muster up the densely textured rock collages of Physical Graffiti, which would usher in the final phase of the group’s career, and it’s extraordinary to follow along with them on the journey that got them there.​